Conventionally, window glass and bodies of transportation devices and window glass or outer walls of high-rise buildings are surface treated for water repellency, oil repellency or hydrophylicity in order to prevent stain. Particularly recently, the surfaces of flat-screen television sets, mobile phones, touch panels, car-navigation equipments, and portable audio players are given “stainproof” treatment or “stain easy to be removed” treatment for better appearance or visibility.
Visual devices are generally equipped with an anti-reflection film on the surface. The anti-reflection film is easily stained by stain, such as sebum, fingerprint, sweat, spit, and hairdressings. The anti-reflection film has such drawbacks, compared to a simple transparent panel, that the stain changes a degree of surface reflection of the film or that the stain stands out against a background as a white body to make images displayed thereon obscure. Therefore, it has been desired for a long time to provide an anti-reflection film which is good in an stainproof property and a stain-removing property and can keep the stainproof property for a longer time.
Generally, perfluoropolyoxyalkylene group-containing compounds have very small surface free energy, and, therefore, have water- and oil-repellency, an anti-chemical property, a lubrication property, a releasing property, and an stainproof property. Accordingly, the perfluoropolyoxyalkylene group-containing compounds are widely used to utilize their properties as a water- and oil-repellent, stainproof agent for paper and fiber; an anti-oil agent for precision instruments; a sealing agent; a releasing agent; and an stainproof agent and an anti-scratch agent in cosmetics, protection films and optical materials such as lenses, anti-reflection films, and recoding media.
For instance, the perfluoropolyoxyalkylene group-containing silane coupling agent is known which is represented by the following formula. The coupling agent has two or three hydrolysable groups on both ends and, therefore, is good in adhesion to a substrate and the surface which is treated with the afore-mentioned coupling agent is water- and oil-repellent and stain is easily wiped off (patent literature 1).

wherein Rf is a divalent linear perfluoropolyoxyalkylene group, R is an alkyl group having 1 to 4 carbon atoms or a phenyl group, X is a hydrolysable group, b is an integer of from 0 to 2, c is an integer of from 1 to 5, and a is 2 or 3.
Recently, displays of many instruments such as touch panels and various kinds of electronic devices need to be daily wiped to clean. Then, requirements for a surface slipping property and an anti-abrasion property in wiping are becoming stricter. In order to meet such requirements, the present inventors proposed a silane coupling agent containing a perfluoropolyoxyalkylene group having a hydrolysable group at one end (patent literature 2). The inventors also proposed a surface treating agent comprising a perfluoropolyether-polysiloxane copolymer which improves the touch of surface (patent literature 3).
[Patent literature 1] Japanese Patent Application Laid-Open No. 2003-238577
[Patent literature 2] Japanese Patent Application Laid-Open No. 2007-297589
[Patent literature 3] Japanese Patent Application Laid-Open No. 2008-088412